Have Display root ServerWindow origin be (0, 0) for all displays.

services/ui/ws/frame_generator.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "services/ui/ws/frame_generator.h"
 
 #include "base/containers/adapters.h"
 #include "cc/output/compositor_frame.h"
 #include "cc/quads/render_pass.h"
 #include "cc/quads/render_pass_draw_quad.h"
@@ skipping 52 matching lines @@
   draw_timer_.Start(
       FROM_HERE, base::TimeDelta(),
       base::Bind(&FrameGenerator::Draw, weak_factory_.GetWeakPtr()));
 }
 
 void FrameGenerator::Draw() {
   if (!delegate_->GetRootWindow()->visible())
     return;
 
   const ViewportMetrics& metrics = delegate_->GetViewportMetrics();
-  const gfx::Rect& output_rect = metrics.bounds;
+  const gfx::Rect output_rect(metrics.bounds.size());
   dirty_rect_.Intersect(output_rect);
   // TODO(fsamuel): We should add a trace for generating a top level frame.
   cc::CompositorFrame frame(GenerateCompositorFrame(output_rect));
   if (frame.metadata.may_contain_video != may_contain_video_) {
     may_contain_video_ = frame.metadata.may_contain_video;
     // TODO(sad): Schedule notifying observers.
     if (may_contain_video_) {
       // TODO(sad): Start a timer to reset the bit if no new frame with video
       // is submitted 'soon'.
     }
@@ skipping 128 matching lines @@
                  gfx::Rect() /* opaque_rect */,
                  bounds_at_origin /* visible_rect */, true /* needs_blending*/,
                  underlay_surface->id());
     DCHECK(!underlay_surface->may_contain_video());
   }
 }
 
 }  // namespace ws
 
 }  // namespace ui